There are a wide variety of plants that are used as forage and fodder for feeding animals. Common crops include corn, alfalfa, timothy, clover, oats, rye grass, fescue grass, orchard grass, legumes, kale, barley, wheat, sorghum, sudan, canary grass, rhodes grass and mixtures of the foregoing. In addition, there are forages and fodders that are unique to specific geographical regions.
When a forge or fodder crop is harvested, it must be preserved so that it will be available for use in feeding the animals, as required. The preservation method must limit the deterioration of the feed while maximizing retained nutritional value. There are three common alternative methods of preserving forage or fodder crops; sun curing, ensiling or dehydrating. Sun curing is not an option in many part of the world as weather conditions do not permit such curing. The ensiling method of preservation involves fermenting wet forage or fodder in an anaerobic environment. The dehydrating method of preservation involves passing the forage or fodder through dryers to substantially reduce the moisture content. Ensiling provides a number of advantages over both sun curing and dehydrating. Ensiled feed has an aroma and flavour that is attractive to livestock and is moist and tender, which makes it very palatable and easy to digest by livestock. It also retains a higher nutritional value. It has a longer storage life than either dehydrated or sun cured feed, if ensiled and stored properly.
Whether ensiling or dehydrating is used as the method of preservation is often dictated by the distance from the source that the animal feed is to be consumed. Silage has a moisture content of between 35 and 75 percent. Whiles this moisture makes the feed very palatable and easy to digest by livestock, it also makes the feed heavy and bulky, which renders it uneconomical to transport silage over long distances. A further problem in transporting silage over long distances, it that when silage is removed from its anaerobic storage facility and exposed to air, it rapidly spoils. The farther the animal feed is to be consumed from the source, the more likely that dehydrating or, where possible, sun cured processes are used as the method of preservation.